With the increasing ability of non-invasive genetic tests to screen groups of patients at high risk of malignancy and the use of endoscopy to detect small malignancies of the gastrointestinal tract, the management of superficial neoplasma becomes more of a clinical dilemma. The small early carcinoma has traditionally been managed with surgical resection although this is associated with significant morbidity and mortality in the gastrointestinal tract especially the esophagus. Barrett's esophagus is a pre-malignant condition of the esophagus that has been diagnosed more frequently currently. The major issues involved in treating superficial neoplasma include accurate staging, type of therapy, and need for careful follow-up. The first major hurdle in implementing endoscopic therapy has been leaped with the development of endoscopic ultrasonography which allows the accurate staging of localized cancers. The second issue involves the ability of an endoscopic treatment to actually cure the primary malignancy which has been suggested based upon several preliminary studies. Photodynamic therapy has been shown to potentially ablate malignant esophageal tissue in 70% of patients treated. We propose to treat patients with superficial carcinomas within Barrett's esophagus who are not candidates for surgery using optimized photodynamic therapy. One of the major limitations to this therapy is predicting uniformity of results. We propose to control this therapy using novel methods. Drug dosimetry will be controlled using novel techniques include a fluorescence probe and a balloon centering device to control light dosimetry. After treatment, patients will be carefully followed to determine if malignant or dysplastic epithelium return. The patients will not only have standard biopsies but also cytology combined with image cytometry to detect the presence of malignancy and dysplasia.